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Lu, Xiaoming

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Lu

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Xiaoming

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Lu, Xiaoming
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    Facilitation stabilizes moisture-controlled alpine juniper shrublines in the central Tibetan Plateau
    (Elsevier BV, 2015) Wang, Yafeng; Liang, Eryuan; Ellison, Aaron; Lu, Xiaoming; Camarero, J. Julio
    The Tibetan Plateau hosts one of the world's highest undisturbed alpine juniper shrublines. However, little is known about the dynamics of these shrublines in response to climate warming and shrub-to-shrub interactions. Since growth of shrubline junipers is limited more by moisture availability than by low temperatures, we tested if upslope advancement of alpine juniper shrublines was constrained by warmer temperatures and related recent droughts. We also evaluated whether facilitation among neighboring shrubs, as inferred from spatial analyses, influenced shrubline dynamics. Three rectangular plots crossing the Juniperus pingii var. wilsonii shrubline were sampled at elevations from 4810 to 4917 m a.s.l. near the Nam Co Lake, central Tibetan Plateau. Location of each stem and its diameter at the root collar and age were measured. We reconstructed the spatial and temporal shrubline dynamics during the past 350 years using standard dendrochronological methods. Independent, long-term summer temperature reconstructions also were associated with shrub recruitment. Point-pattern analyses were used to characterize spatial patterns of different size classes of shrubs. The three shrublines showed little long-term changes despite ongoing warming; no upward shift has occurred in the past 100 years. Recruitment was negatively associated with summer temperatures and drought occurrence since the 1920s. Spatial patterns were characterized by clustering at local scales and attraction between the different size classes, suggesting facilitation. We conclude that moisture availability limits the recruitment and elevational advance of junipers in this area of the Tibetan Plateau. Dynamics of alpine shrublines are more contingent on positive interactions and local environmental factors than on regional climatic variability.
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    Nitric Oxide Activates Intradomain Disulfide Bond Formation in the Kinase Loop of Akt1/PKBα after Burn Injury
    (D.A. Spandidos, 2013) Lu, Xiaoming; Tompkins, Ronald; FISCHMAN, A.J.
    Severe burn injury is an acute inflammatory state with massive alterations in gene expression and levels of growth factors, cytokines and free radicals. During the catabolic processes, changes in insulin sensitivity and skeletal muscle wasting (unintended loss of 5–15% of lean body mass) are observed clinically. Here, we reveal a novel molecular mechanism of Akt1/protein kinase Bα (Akt1/PKBα) regulated via cross-talking between dephosphorylation of Thr308 and S-nitrosylation of Cys296 post severe burn injury, which were characterized using nano-LC interfaced with tandem quadrupole time-of-fight mass spectrometry (Q-TOF)micro tandem mass spectrometry in both in vitro and in vivo studies. For the in vitro studies, Akt1/PKBα was S-nitrosylated with S-nitrosoglutathione and derivatized by three methods. The derivatives were isolated by SDS-PAGE, trypsinized and analyzed by the tandem MS. For the in vivo studies, Akt1/PKBα in muscle lysates from burned rats was immuno-precipitated, derivatized with HPDP-Biotin and analyzed as above. The studies demonstrated that the NO free radical reacts with the free thiol of Cys296 to produce a Cys296-SNO intermediate which accelerates interaction with Cys310 to form Cys296-Cys310 in the kinase loop. MS/MS sequence analysis indicated that the dipeptide, linked via Cys296-Cys310, underwent dephosphorylation at Thr308. These effects were not observed in lysates from sham animals. As a result of this dual effect of burn injury, the loose conformation that is slightly stabilized by the Lys297-Thr308 salt bridge may be replaced by a more rigid structure which may block substrate access. Together with the findings of our previous report concerning mild IRS-1 integrity changes post burn, it is reasonable to conclude that the impaired Akt1/PKBα has a major impact on FOXO3 subcellular distribution and activities.